maybe they are on an iphone or dan android pc. you want to give each person the best possible handful of pieces of content for them at that time. that is a growing problem. it is during free quickly and we believe it is important to solve. there is a bunch of machine learning, a bunch of infrastructure to assemble for each person. one thing i think about this is your publishing for each of $1 billion ever met. in needs to stab today. there is a model that tries to project is most likely to get air active with optimizing -- news feed optimizes what they would like to interact with. what will create a consumer of between the publisher and consumer? that is the high level. >> you think about how that system works for. lettis positive feedback. you'll get more of that thing. how do you tweak the algorithms so people ill don't show up -- it is a personalized newspaper. how do you now the difference between how they interact. people want to have both interactive, one more often but they want to see the other one and check it out occasio